Insulin and circadian rhythm genes of the Nile rat (Arvicanthis niloticus) are conserved and orthologous to those in the rat, mouse and human

The African grass or Nile rat (NR) (Arvicanthis niloticus) is a herbivorous diurnal rodent which is used as a biological model for research on type 2 diabetes mellitus (T2DM) and the circadian rhythm. Similar to humans, male NRs develop T2DM with high-carbohydrate diets. The NR thus provides a unique opportunity to identify the nutritional and underlying genetic factors that characterise human T2DM, as well as the effects of potential anti-diabetic phytochemicals such as Water-Soluble Palm Fruit Extract. Whole genome sequencing (WGS) could help identify possible genetic causes why NRs spontaneously develop T2DM in captivity. In this study, we performed WGS on a hepatic deoxyribonucleic acid (DNA) sample isolated from a male NR using PacBio high-fidelity long-read sequencing. The WGS data obtained were then de novo assembled and annotated using PacBio HiFi isoform sequencing (Iso-Seq) data as well as previous Illumina RNA sequencing (RNA-Seq) data. Genes related to insulin and circadian rhythm pathways were present in the NR genome, similar to orthologues in the rat, mouse and human genomes. T2DM development in the NR is thus most likely not attributable to structural differences in these genes when compared to other biological models. Further studies are warranted to gain additional insights on the genetic-environmental factors which underlie the genetic permissiveness of NRs to develop T2DM.

Impact of COVID-19 on healthcare utilization, cases, and deaths of citizens and displaced Venezuelans in Colombia: Complementary comprehensive and safety-net systems under Colombia's constitutional commitment

OBJECTIVE

Colombia hosts 1.8 million displaced Venezuelans, the second highest number of displaced persons globally. Colombia's constitution entitles all residents, including migrants, to life-saving health care, but actual performance data are rare. This study assessed Colombia's COVID-era achievements.

METHODS

We compared utilization of comprehensive (primarily consultations) and safety-net (primarily hospitalization) services, COVID-19 case rates, and mortality between Colombian citizens and Venezuelans in Colombia across 60 municipalities (local governments). We employed ratios, log transformations, correlations, and regressions using national databases for population, health services, disease surveillance, and deaths. We analyzed March through November 2020 (during COVID-19) and the corresponding months in 2019 (pre-COVID-19).

RESULTS

Compared to Venezuelans, Colombians used vastly more comprehensive services than Venezuelans (608% more consultations), in part due to their 25-fold higher enrollment rates in contributory insurance. For safety-net services, however, the gap in utilization was smaller and narrowed. From 2019 to 2020, Colombians' hospitalization rate per person declined by 37% compared to Venezuelans' 24%. In 2020, Colombians had only moderately (55%) more hospitalizations per person than Venezuelans. In 2020, rates by municipality between Colombians and Venezuelans were positively correlated for consultations (r = 0.28, p = 0.04) but uncorrelated for hospitalizations (r = 0.10, p = 0.46). From 2019 to 2020, Colombians' age-adjusted mortality rate rose by 26% while Venezuelans' rate fell by 11%, strengthening Venezuelans' mortality advantage to 14.5-fold.

CONCLUSIONS

The contrasting patterns between comprehensive and safety net services suggest that the complementary systems behaved independently. Venezuelans' lower 2019 mortality rate likely reflects the healthy migrant effect (selective migration) and Colombia's safety net healthcare system providing Venezuelans with reasonable access to life-saving treatment. However, in 2020, Venezuelans still faced large gaps in utilization of comprehensive services. Colombia's 2021 authorization of 10-year residence to most Venezuelans is encouraging, but additional policy changes are recommended to further integrate Venezuelans into the Colombian health care system.

Cas9-mediated endogenous plasmid loss in Borrelia burgdorferi

The spirochete Borrelia burgdorferi, which causes Lyme disease, has the most segmented genome among known bacteria. In addition to a linear chromosome, the B. burgdorferi genome contains over 20 linear and circular endogenous plasmids. While many of these plasmids are dispensable under in vitro culture conditions, they are maintained during the natural life cycle of the pathogen. Plasmid-encoded functions are required for colonization of the tick vector, transmission to the vertebrate host, and evasion of host immune defenses. Different Borrelia strains can vary substantially in the type of plasmids they carry. The gene composition within the same type of plasmid can also differ from strain to strain, impeding the inference of plasmid function from one strain to another. To facilitate the investigation of the role of specific B. burgdorferi plasmids, we developed a Cas9-based approach that targets a plasmid for removal. As a proof-of-principle, we showed that targeting wild-type Cas9 to several loci on the endogenous plasmids lp25 or lp28-1 of the B. burgdorferi type strain B31 results in sgRNA-specific plasmid loss even when homologous sequences (i.e., potential sequence donors for DNA recombination) are present nearby. Cas9 nickase versions, Cas9D10A or Cas9H840A, also cause plasmid loss, though not as robustly. Thus, sgRNA-directed Cas9 DNA cleavage provides a highly efficient way to eliminate B. burgdorferi endogenous plasmids that are non-essential in axenic culture.

“Saturday Night Seder” and the Affordances of Cultural Arts during COVID-19

Saturday Night Seder (SNS) was broadcast online on 11 April 2020 as a public celebration of Passover and as a benefit for the Centers for Disease Control and Prevention (CDC) Foundation. Part seder, part telethon, and part Broadway theatrical performance, SNS was the first online event to create a national Jewish communal gathering space in the context of coronavirus disease 2019 (COVID-19) and has since been viewed over 1.5 million times. This article examines SNS as a uniquely situated manifestation of COVID-19, and draws attention to the various affordances engendered by SNS for Jewish gathering, learning, and exchange. It draws upon interviews with members of the production team, featured participants, and expert informants, as well as viewer responses from Twitter and YouTube: a dataset that includes 2000 tweets and over 1800 YouTube comments. Collectively, these data suggest that cultural arts productions such as SNS have afforded an expansive network of online Jewish conversations during COVID-19, and have invited a broad audience of Jews and non-Jews into dialogue over Jewish themes and content.

Twinfilin bypasses assembly conditions and actin filament aging to drive barbed end depolymerization

Cellular actin networks grow by ATP-actin addition at filament barbed ends and have long been presumed to depolymerize at their pointed ends, primarily after filaments undergo "aging" (ATP hydrolysis and Pi release). The cytosol contains high levels of actin monomers, which favors assembly over disassembly, and barbed ends are enriched in ADP-Pi actin. For these reasons, the potential for a barbed end depolymerization mechanism in cells has received little attention. Here, using microfluidics-assisted TIRF microscopy, we show that mouse twinfilin, a member of the ADF-homology family, induces depolymerization of ADP-Pi barbed ends even under assembly-promoting conditions. Indeed, we observe in single reactions containing micromolar concentrations of actin monomers the simultaneous rapid elongation of formin-bound barbed ends and twinfilin-induced depolymerization of free barbed ends. The data show that twinfilin catalyzes dissociation of subunits from ADP-Pi barbed ends and thereby bypasses filament aging prerequisites to disassemble newly polymerized actin filaments.

Haloferax volcanii Immersed Liquid Biofilms Develop Independently of Known Biofilm Machineries and Exhibit Rapid Honeycomb Pattern Formation

The ability to form biofilms is shared by many microorganisms, including archaea. Cells in a biofilm are encased in extracellular polymeric substances that typically include polysaccharides, proteins, and extracellular DNA, conferring protection while providing a structure that allows for optimal nutrient flow. In many bacteria, flagella and evolutionarily conserved type IV pili are required for the formation of biofilms on solid surfaces or floating at the air-liquid interface of liquid media. Similarly, in many archaea it has been demonstrated that type IV pili and, in a subset of these species, archaella are required for biofilm formation on solid surfaces. Additionally, in the model archaeon Haloferax volcanii, chemotaxis and AglB-dependent glycosylation play important roles in this process. H. volcanii also forms immersed biofilms in liquid cultures poured into petri dishes. This study reveals that mutants of this haloarchaeon that interfere with the biosynthesis of type IV pili or archaella, as well as a chemotaxis-targeting transposon and aglB deletion mutants, lack obvious defects in biofilms formed in liquid cultures. Strikingly, we have observed that these liquid-based biofilms are capable of rearrangement into honeycomb-like patterns that rapidly form upon removal of the petri dish lid, a phenomenon that is not dependent on changes in light or oxygen concentration but can be induced by controlled reduction of humidity. Taken together, this study demonstrates that H. volcanii requires novel, unidentified strategies for immersed liquid biofilm formation and also exhibits rapid structural rearrangements.IMPORTANCE This first molecular biological study of archaeal immersed liquid biofilms advances our basic biological understanding of the model archaeon Haloferax volcanii Data gleaned from this study also provide an invaluable foundation for future studies to uncover components required for immersed liquid biofilms in this haloarchaeon and also potentially for liquid biofilm formation in general, which is poorly understood compared to the formation of biofilms on surfaces. Moreover, this first description of rapid honeycomb pattern formation is likely to yield novel insights into the underlying structural architecture of extracellular polymeric substances and cells within immersed liquid biofilms.